Extreme pressure lubricants



' Patented Jan. 10,1950

UNITED STATES PATENT OFFICE ration of Delaware No Drawing. ApplicationApril 7, 1948, Serial No. 19,630

9 Claims. (Cl. 252-46.?)

The present invention relates to extreme pressure lubricants and moreparticularly to additives which may be combined with various lubricatingoils, greases, and the like, to impart extreme pressure propertiesthereto, and to methods of preparing such additives.

In the lubrication of modern machinery it is frequently necessary toprovide lubricants having higher load bearing capacities than areprovided by ordinary mineral oil products. Underconditions of extremepressure it has been found necessary to provide certain additivecompositions for lubricating oils and greases which are effective toprevent metal to metal contact between parts being lubricated underconditions where the unusual pressures encountered would cause failureof ordinary lubricating films.

Various compounds, usually including materials such as sulfur, chlorine,phosphorus, and the like, have been included in extreme pressurelubricents and are usually compounded in such a way that they arerelatively inactive at ordinary temperaturesl These materials becomeactive, however, when conditions arise, such as the application ofextreme pressure between moving parts, etc., which result in elevatedtemperatures. For example, when the normal lubricating oil film beginsto break between two metallic parts, such, for example, as opposed gearelements operating under heavy load, high friction results which, ofcourse, causes an increase in temperature at the point or area ofcontact. This causes a chemical reaction between the extreme pressurematerial and the metal parts involved to deposit on the latter a verythin but highly protective film of metal sulfide, metal chloride, ormetal phosphide, etc.

The use of halogens, especially chlorine, and/or sulfur, and/orphosphorus compositions in oils and greases for the purposes referred toabove is well known in the art. It is also known that certain organiccompounds including some or all of these materials are effective extremepressure additives for lubricants. In general, the

prior art compositions used for imparting extreme pressure properties tolubricating compositions fall into two classes. One class includescertain sulfur-chlorine organic extreme pressure compositions which havebeen found to be quite effective for carrying moderate loads at high 2 5speeds. These compositions maysubstitute or add phosphorus also. Suchlubricants give good test results on the SAE extreme pressure testingmachine and are quite satisfactory for the lubricating of passenger carsand light trucks. When tested on the Timken lubricant and wear testmachine, however, the prior art compositions of the high speed typecarry relatively poor loads and are found to be inadequate for properlubrication in heavy truck operations under conditions where low speedand high torque prevail.

Another class of compounds, commonly used in the prior art, includesother sulfur phosphorus products and may also include chlorine in somecases. Some of these are quite satisfactory for heavy truck duty,frequently being capable of carrying high loads on the Timken machine.These prior art compounds, .however, are somewhat less satisfactory forhigh speed operation. for example, in the lubrication of passengerautomobiles, and they are found to give low test results on the SAEmachine.

The present invention is based upon the discovery that certain organicester derivatives which include phosphorus and halogens, and preferablyalso contain sulfur, are effective extreme pressure agents at both highand low speeds. According to this invention, halogenated este rs ofcyclic carboxylic acids or substituted cyclic carboxylic acids arereacted with an alkali salt of an alkyl, alkenyl, aryl or aralkylthiophosphoric or thiophosphorous acid to yield materials which containall three of the desirable constituents, halogen, sulfur, andphosphorus. The relative chemical activities of these ingredients, inthe compositions of this invention, appear to be well adjusted to meetthe lubrication needs of widely diiierent operating conditions. Thecyclic or substituted cyclic carboxylic acids in the esters may includesaturated and unsaturated alicyclic rings and substituted benzenoidrings. Some of these types are described below under Example I.

More specifically, the invention comprises the halogenation, forexample, chlorination of rosin esters, hydrogenated rosin, methylatedrosin, or

partly hydrogenated and/or methylated rosin de-- rivatives and/ormixtures thereof. This may be carried out by introducing gaseouschlorine, or liquid bromine, into the rosin derivative at a suitabletemperature, within the range, for example,

3 of 70 to 250 F. The hydrogenated material is then reacted with asuitable salt, for example, an alkali metal salt such as the sodium saltof an alkoxy thio acid of phosphorus. The products are prepared byhalogenating the rosin or rosin derivative first and then reacting toform the ester. The alkoxy group on the thio acid preferably is a shortchain, branched, or linear, having 1 to about 8 carbon atoms. Isopropyl,butyl, isobutyl, isoamyl groups, and the like are satisfactory.Materials so prepared have been found very useful in the preparation oigeneral purpose lubricants having excellent and unexpected extremepressure properties under extremely diflerent and diillcult lubricatingconditions.

Example I A commercial mixture ofmethyl esters of rosin having thegeneral approximate formula, CuHaoCOOCI-Is, was chlorinated by passinggaseous chlorine through the ester at a temperature of 150 to 160 F. toa final chlorine content of 19.96%. The rosin esters used are more fullydescribed below. The esters are in the form of a viscous pale yellowliquid which appears to contain about 84% of a mixture of the methylesters 01! several isometric forms of abietic acid. The ester materialis a proprietary product of the Hercules Powder Company sold under thetrade name Abalyn." It is classifled as a methyl abietate having an acidnumber of about 5, a saponiflcation number of about 18 to 50, the sampletested having a number of 25, and a'boiling point of about 360 to 365 C.

An alkoxy thiophosphoric acid, specifically diisopropyl dithiophosphoricacid, was prepared as follows:

480 grams of 99% isopropyl alcohol were placed in a glass flask equippedwith a stirrer and reflux condenser. 444 grams of phophorus pentasulflde(Pass) were added in about ten equal portions over a period of 15minutes. The temperature rose spontaneously to. about 120 F., and heatwas then applied, and refluxing began at 130 F. As the reactionproceeded, the temperature was raised to 210 F. and held at this'pointfor two hours, at which time no refluxing could be observed, indicatingsubstantially complete con- 7 version of the alcohol to thedithiophosphoric acid. The product was then cooled and filtered,

and was found to contain 14.76% phosphorus and 28.56% sulfur.corresponding approximately to the following formula:

CM B

(Theoretical r-issgt, s-zaeqa) The quantity of dithiophosphate wasselected in this case so as to react with approximately oneseventh ofthe chlorinated esters. and the final product therefore consisted ofabout 6 mols of chlorinated ester to one moi of the thiophosphatecondensation product.

It will be understood, of course, that the proportions oi thiophosphateand chlorinated esters may be varied over a wide range. Thus moi ratioof thiophosphate to chlorinated esters may vary from about 1:50 to about2:1, the latter case representing complete reaction between the sodiumsalt and all the chlorine in the particular dichloro esters here used.When a higher proportion of chlorine is added to the original esters,even higher moi ratios of thiophosphate to chloro ester may be used.

The product thus obtained was a clear brown oily liquid, having thefollowing analysis:

Per cent Phosphorus 1 43 Sulfur 2 56 Chlorine 14,19

It is believed that the condensation reaction proceeds according to thefollowing equation:

s 00.111 /Cl NaCl a OCaHi Approximate composition of commercial rosinesters Per cent Methyl esters of abietic and neoabietic acid (contain 2conJugated double bonds per -mol). 23

Methyl ester of dihydroabietic acid (contains 1 double bond per mol) 22Methyl ester of tetrahydroabietic acid Methyl ester of dehydroabieticacid (contains one benzenoid ring) 1'l' Unsaponiflable matter uctdescribed above was prepared in SAE 90 grade phoric acid prepared asabove, were mixed with a 540 grams of isopropyl alcohol (91%) as asolvent and 11 grams NaOH dissolyedin 33' grams of water. The mixturewas stirred and heated to reflux (178 F.) to promote reaction and thencooled to 120 F. Thereafter 540 grams of chlori-' nated ester preparedas above were added and heating was continued with refluxing for fourhours. The alcohol and water were then. stripped 01;! under vacuum.andthe remaining product was filtered. Obviously other aliphaticalcohols may be used in lieu of isopropyl, those of 2 to about 10 carbonatoms being preferred.

mineral lubricating oil having the following characteristics:

Mineral oil components 3 BtockA Stock]! 1 so so Refining method 8Gravity, API 21.9 29.8 ms ass as Via/ 4809.4 376.1 yrs 210, ma 58.0VI.... 86 Con. Carbon..- 2.86 0.07 Sulfur 0.02 0.34

l Mid-Continent.

Propane extracted. I Phenol extracted.

Tests on the Timken and SAE machines showed the product to have-excellent extreme pressure properties and these properties wereimproved even further by the addition of a small amount of tricresylphosphate. The results of tests on the Timken and SAE machines are shownin the following:

ing compositions containing the extreme pressure additive describedabove may contain other materials such as oiliness agents, antioxidants,

Table I 'limken Machine SAE ti tt Additives In ass so on) 2 i Sear WidthUnit Load gg' ggg Levr) (in $6. In.) (Lhs./Sq.ln.) M

N one (Mineral oil only) 1 1- 65 7, 350 10% Above Product 43 1.5 36, 800360 10% Above Product 'Iricresyl Phosphate 68 2.05 42, 500

It is to be understood that this invention is not limited to theparticular esters, nor to the particular thiophosphoric acid referred toabove, but may be applied to a great variety of esters andthiophosphoric acids. For example, it is shown in copending applicationSerial No. 9,617 filed February 19, 1948, by L. A. Mikeska and thepresent applicant, that dithiophosphoric acids derived fromditertiaryoctyl phenol, ditertiary octyl phenol sulfide, and similar aryl andalkaryl hydroxy compounds can be used successfully in carrying out thisreaction. It is also shown in the same application that esters ofglycerin (for example, lard oil) and of monohydroxy alcohols (forexample, sperm oil) are equally effective. It is therefore apparent thatthe essential limitations on the type of cyclic ester which may be usedare as follows:

(1) It must react with halogens to form addition or substitutionproducts capable of further reaction with an alkali salt. This includesboth saturated and unsaturated rings except benzenoid rings, the latterbeing specifically excluded. It also includes alkyl and alkenyl(straight and branched chain) substituted rings whether benzenoid ornot.

(2) The final condensation product must be relatively non-volatile attemperatures up to about 200 F.

(3) The final condensation product must be soluble in mineral oils tothe extent of at least 1%. In general, this includes cyclic estershaving molecular weights between about 150 and 2000.

Other halogens than chlorine, for example, bromine, may be employed toproduce the halogenated esters. Likewise, in lieu of dithiophosphoricacids, the corresponding dithiophosphorous acids, or mixtures of thesemay be used. The proportions of reactive materials to be included in theadditive composition per se should lie within th following limits:

Per cent Chlorine About 5 to 50 Thiophosphate About 1 to Final product(additive) Per cent 0.1-2.5 s 0.2-5 Cl- 4-40 suitable proportions andwith various lubricating oils as will be understood by those skilled inthe art. It will be understood further that lubricat corrosioninhibitors, viscosity index improvers, and the like.

The composition of this invention may be marketed as a concentrate, e.g. about 10% to in-a suitable solvent, which may be a lube oil ofparaifinic, naphthenic, or other type. or other solvents such as xylene,kerosene, and the like. The use of 0.05 to 5.0% (on the basis offinished lubricant) of a separate phosphorus-containing composition suchas tricresyl phosphate, tricresyl phosphite, and other organicderivatives of acids of phosphorus appears to augment the effectivenessof additives of the general type described above without increasingtheir corrosivity toward metals while at the same time improving theoilness characteristics of the lubricant. For this reason the use oftricresyl phosphate, phosphite, and related materials, is recommendedbut is not essential inasmuch as the reaction product described above isa very efiective extreme pressure agent in and of itself. Theeffectiveness of the agent appears to be due to the fact that itcombines the load-carrying capacity of halogen, preferably chlorine,with those of sulfur and phosphorus. At the same time the compositionappears to have good oilness characteristics and to possess otherpropetries which are desirable in lubricants of the extreme pressuretype.

The composition of this invention is not to be confused with thatdescribed in U. S. Patent No. 2,347,592 to Cook and Thomas whichdescribes hydrogenated abietyl alcohol esters of dithiophosphoric acidused as corrosion inhibitors. The present composition has the generalformula where R1 is a rosin ester as described above, preferablyhalogenated, chlorine being the preferred halogen, the halogen contentbeing preferably such as to provide 4 to 40%, preferably 5 to 20%,chlorine or other halogen in the product; R3 and R3 are similar ordissimilar alkyl hydrocarbon groups of straight or branched chain.preferably saturated and preferably of 2 to 10 carbon atoms.

The lubricating oil in which this additive may and Ba are aliphatichydrocarbon groups of 2 to 10 carbon atoms each.

2. Composition as in claim 1 wherein R1 is a chlorinated rosin ester.

3. Composition as in claim 1 wherein R1 is chlorinated methyl 'abietate.

4. A lubricating composition consisting essentially of petroleum baseoil of lubricating viscosity containing 1 to 20% by weight 01 a materialhaving the general formula wherein R1 is a halogenated rosin ester, andR2.

obtain a condensation product of said halogenated ester and said thiosalt.

8. The process which comprises chlorinating methylated rosin acids to achlorine content of 5 to 50% by weight and thereafter reacting an alkoxydithiophosphoric acid salt of an alkali metal with said chlorinatedmaterial to produce a condensation product containing active chlorine,sulfur and phosphorus.

9. The method of preparing an extreme pressure additive for mineral oilbase lubricants which comprises chlorinating a commercial rosin esterconsisting predominantly of methyl esters of abietic acids at atemperature of the range of about 70 to 250 F. to a chlorine content ofthe order of 5 to 50% by weight, neutralizing isopropyldi-thlophosphoric acid with sodium hydroxide, and condensing theisopropyl dithiophosphate and the chlorinated ester at a temperature ofabout 178 F.

ELlillER B. CYPHERS.

REFERENCES CITED UNITED STATES PATENTS Name Date Engelke June 12, 1945Number aarma'zo

4. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF PETROLEUM BASEOIL OF LUBRICATING VISCOSITY CONTAINING 1 TO 20% BY WEIGHT OF A MATERIALHAVING THE GENERAL FORMULA